Thousands of Cambodians in Thailand returned home as border crossings were closed amid an escalating border dispute, which has seen at least 14 civilians and two soldiers.

Around 3,000 Cambodian workers flocked to the Ban Laem border checkpoint in Chanthaburi province on July 25.

The mass exodus came after the Chanthaburi Marine Corps Task Force issued a special order allowing temporary cross-border travel between 9 am and 3 pm.

Thai authorities earlier sealed land crossings into neighbouring Cambodia as fresh military violence erupted along the border on Thursday morning.

Cambodian artillery strikes had hit a series of locations across Surin and Si Sa Ket, including a 7-Eleven convenience store, while Thailand responded with airstrikes on Thursday morning.

The escalating military confrontation - the bloodiest in more than a decade - flared in long-disputed border areas as both sides accused each other of instigating the violence.

Thai Health Minister Somsak Thepsuthin said at least 15 people, including a soldier and two children Bandit Aunjit and Namkhong Boontang aged seven and eight, were killed in the crossfire, while some 32 were injured.

A provincial officer in Cambodia's Oddar Meanchey province confirmed one person was wounded and five killed in Thai attacks.

More than 120,000 residents on both sides of the border have fled as the fighting continued to rage today.

The Royal Thai Army reported that Thai military officers at Prasat Ta Muen temple in Surin heard the sound of an unmanned aerial vehicle at 7:35 am but could not pinpoint its location.

Six armed Cambodian soldiers, including one with an RPG, then approached the barbed wire area in front of the Thai base, prompting Thai soldiers to shout at them to stop.

At 8:20 am, the Cambodian side reportedly fired in the opposite direction of the base to the east of the castle before artillery fire was launched around 9 am.

Jirayu Huangsap, spokesman for the Prime Minister's Office, said the government received military information and 'clear evidence' that the Cambodian side initiated the attack.

However, Cambodian PM Hun Manet said Thailand initiated the attack, forcing him to retaliate.

Cambodian troops reportedly fired continuous artillery rounds using 122mm rockets from BM-21 rocket launchers at residents in Surin, where one civilian was killed and a five-year-old child and his family were severely injured. Seven soldiers were also injured in the rocket strike.

The Thai army closed all border checkpoints at 8 am, while the Ministry of Foreign Affairs was instructed to compile evidence of the alleged provocations from the Cambodian side to lodge a formal complaint with international organisations.

The Royal Thai Embassy in Phnom Penh has advised Thai residents in Cambodia to leave as soon as possible. It also urged the public to avoid non-essential travel to Cambodia until the situation is resolved.

The Cambodian Ministry of National Defence condemned Thailand for alleged encroachment.

Prime Minister Hun Manet said Cambodia 'had no choice' but to respond with its armed forces against 'armed aggression'.

The clash flared several days after a border landmine exploded, injuring three Thai soldiers, including one who lost a leg.

Tensions between Thailand and Cambodia escalated after a clash between troops from both countries in a disputed area in Nam Yuen district, Ubon Ratchathani, on May 28, resulting in the death of a Cambodian sergeant.

Thailand expressed its intention to resolve the dispute through existing bilateral mechanisms. However, Cambodia vowed to take the case before the International Court of Justice in The Hague.